The invention relates to a process for the preparation of washing- and cleaning-active surfactant-containing granules with a bulk density above 500 g/l from a surfactant preparation form which has a non-surface-active liquid component, in particular water, and which, at atmospheric pressure and temperatures between 20 and 80xc2x0 C., is in liquid to paste form, by granulation and simultaneous drying in a fluidized bed above an inflow base provided with openings for the fluidization gas, in particular fluidization air, where the term drying means the partial or complete removal of the non-surface-active liquid component.
Such a process is known from European Patent Specification 0 603 207 B1 from the Applicant. The inflow base and the size and shape of its openings can vary, as has already been shown in detail in said patent specification.
In this known process, it is the case time and again, in particular when operation is interrupted, that granules fall through the openings of the inflow base into the particularly hot area below the base, where they are thermally damaged and discolored, and some pass back through the openings of the inflow base into the fluidized bed, meaning that the final product comprises white granules with brown to black spots, making the product overall unsuitable for use. If the particles which have fallen down through the inflow base remain in this hot area, then after each time the plant has been out of service it is necessary to clean this inflow zone and also the base itself to which these particles adhere, and this is time-consuming.
The problems arise particularly during the preparation of granules with particularly high bulk densities above 500 g/l. Sometimes even during operation, these particularly heavy particles drop against the fluidizing air through the openings in the inflow base into the lower hot area, from which they are blown back into the fluidized bed by the fluidizing air following thermal decomposition and breakage.
A particularly weighty problem in the case of the preparation of granules with particularly high bulk densities according to the known process is the baking-on of the hot granules, which are tacky because of their surfactant content, on the inflow base and in the region of its openings, where they gradually narrow the free cross section until the aeration for the fluidization gas can no longer compensate for the pressure loss resulting in this manner. The unit must be switched off at this point in time at the latest and the inflow base must be freed from the partially thermally decomposed cakings, which is very time-consuming.
The object of the invention was therefore to improve the efficiency of the process of the type mentioned in the introduction. In particular, the aim is to considerably prolong the duration of uninterrupted operation of a corresponding unit. Moreover, the intention is to improve the quality of the resulting product such that the danger of black or brown spots (xe2x80x9cspecksxe2x80x9d) on the preferably white granules no longer occurs.